All respondents born outside the United States were asked for the year in which they came to live in the United States. This includes people born in Puerto Rico and U.S. Island Areas; people born abroad of an U.S. citizen parent or parents; and the foreign born. (See "Citizenship Status.") For the Puerto Rico Community Survey, respondents were asked for the year in which they came to live in Puerto Rico.

Respondents were directed to indicate the year they entered the U.S. (or Puerto Rico, for the Puerto Community Survey) "to live." For respondents who have entered the U.S. (or Puerto Rico for the Puerto Rico Community Survey) multiple times, the interviewers were instructed to request the most recent year of entry. For respondents who either did not ask the interviewer for clarification or for those who mailed back the questionnaire without being interviewed in person, it was difficult to ensure that respondents interpreted the question as intended.

Beginning in 2006, the population in group quarters (GQ) is included in the ACS. Some types of GQ populations may have year of entry distributions that are different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the year of entry distribution. This is particularly true for areas with a substantial GQ population.

The data on citizenship status were derived from answers to Question 8. The responses to this question were used to determine the U.S. citizen and non-U.S. citizen populations as well as to determine the native and foreign-born populations. Respondents were asked to select one of five categories:

(1) born in the United States,
(2) born in Puerto Rico, Guam, the U.S. Virgin Islands, or Northern Marianas,
(3) born abroad of U.S. citizen parent or parents,
(4) U.S. citizen by naturalization, or
(5) not a U.S citizen. Respondents indicating they are a U.S. citizen by naturalization are also asked to print their year of naturalization. People born in American Samoa, although not explicitly listed, are included in the second response category.

For the Puerto Rico Community Survey, respondents were asked to select one of five categories:
(1) born in Puerto Rico,
(2) born in a U.S. state, District of Columbia, Guam, the U.S. Virgin Islands, or Northern Marianas,
(3) born abroad of U.S. citizen parent or parents,
(4) U.S. citizen by naturalization, or
(5) not a U.S. citizen. Respondents indicating they are a U.S. citizen by naturalization are also asked to print their year of naturalization. People born in American Samoa, although not explicitly listed, are included in the second response category.

When no information on citizenship status was reported for a person, information for other household members, if available, was used to assign a citizenship status to the respondent. All cases of nonresponse that were not assigned a citizenship status based on information from other household members were allocated the citizenship status of another person with similar characteristics who provided complete information. In cases of conflicting responses, place of birth information is used to edit citizenship status. For example, if a respondent states he or she was born in Puerto Rico but was not a U.S. citizen, the edits use the response to the place of birth question to change the respondents status to "U.S. citizen at birth."

Respondents who indicated that they were born in the United States, Puerto Rico, a U.S. Island Area (such as Guam), or abroad of American (U.S. citizen) parent or parents are considered U.S. citizens at birth. Foreign-born people who indicated that they were U.S. citizens through naturalization also are considered U.S. citizens.

The native population includes anyone who was a U.S. citizen or a U.S. national at birth. This includes respondents who indicated they were born in the United States, Puerto Rico, a U.S. Island Area (such as Guam), or abroad of American (U.S. citizen) parent or parents.

The foreign-born population includes anyone who was not a U.S. citizen or a U.S. national at birth. This includes respondents who indicated they were a U.S. citizen by naturalization or not a U.S. citizen. The American Community Survey questionnaires do not ask about immigration status. The population surveyed includes all people who indicated that the United States was their usual place of residence on the survey date. The foreign-born population includes naturalized U.S. citizens, Lawful Permanent Residents (immigrants), temporary migrants (e.g., foreign students), humanitarian migrants (e.g., refugees), and unauthorized migrants (people illegally present in the United States).

Beginning in 2006, the population in group quarters (GQ) is included in the ACS. Some types of GQ populations may have citizenship status distributions that are different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the citizenship status distribution. This is particularly true for areas with a substantial GQ population.

In the 1996-1998 American Community Survey, the third response category was "Yes, born abroad of American parent(s)." However, since 1999 in the American Community Surveys and since the 2005 Puerto Rico Community Surveys, the response category was "Yes, born abroad of American parent or parents." In 2008, respondents who indicated that they were a U.S. citizen by naturalization were also asked to print their year of naturalization. Also in 2008, modifications in wording were made to both the third response category (changed from Yes, born abroad of American parent or parents." to "Yes, born abroad of U.S. citizen parent or parents.") and the fifth response category (changed from "No, not a citizen of the United States" to "No, not a U.S. citizen").

Excerpt from:

Social Explorer; U.S. Census Bureau; American Community Survey 2006-2008 Summary File: Technical Documentation.